Various types of auditory prosthesis systems have been developed to assist patients who have severe (e.g., complete) hearing loss. For example, cochlear implant systems may provide a sense of hearing for sensorineural hearing loss patients by providing electrical stimulation representative of sound directly to stimulation sites within the cochlea. As another example, electro-acoustic stimulation (“EAS”) systems may assist patients with some degree of residual hearing in the low frequencies (e.g., below 1000 Hz) by providing acoustic stimulation representative of low frequency audio content and electrical stimulation representative of high frequency content.
Many auditory prosthesis systems include a sound processor apparatus (e.g., a behind-the-ear (“BTE”) sound processing unit, a body worn device, etc.) configured to be located external to the patient. The sound processor apparatus may perform a variety of functions, such as processing audio signals presented to the patient, controlling an operation one or more implantable devices (e.g., one or more cochlear implants), and providing power to the one or more implantable devices.
Audio signals presented to the patient are initially detected by a microphone located near the ear of the patient, such as mounted to an ear hook coupled to a housing that houses the sound processor. In order to properly detect sound, at least a portion of the microphone typically must be exposed to the environment. As a result, the microphone is exposed to many environmental contaminants such as skin, earwax, perspiration, and the like. The environmental contaminants and ordinary wear due to continued operation may cause the microphone to degrade. Degradation may manifest itself as a general decrease in sensitivity (e.g., drift) as well as a change in the frequency response of the microphone.
For small children especially, this degradation can be difficult to detect. Where the degradation affects the intelligibility of speech, the learning and language development of children can be affected. For patients in general, the degradation may occur slowly over time and therefore not be perceptible.